The present invention relates generally to an automotive audio system with a plurality of speakers installed within a vehicular compartment. More specifically, the invention relates to an automotive multi-speaker audio system which can generate good audio sound for listeners in any vehicular seat within the compartment.
In modern automotive vehicles, built-in vehicle-mountable audio system, i.e. radios, magnetic tape players, compact disk players and so forth have become very popular. In addition, these automotive audio systems produce higher- and higher-quality audio sound. Various relatively high-quality, expensive systems have been developed and put on the market.
So-called ambience control systems which adjust the volumes and phases among the speakers in multi-speaker systems have recently become an additional feature. Conventional ambience control systems simply adjust the reproduction volume level at each speaker in order to control interference among acoustical vibrations in the vehicle compartment and so shift the acoustical vibration center to just above a single listener or distributing the acoustical vibration centers among multiple listeners.
Such conventional ambience control systems are commercially successful, as they provide a reasonable or at least acceptable level of audio sound. However, since such conventional ambience control systems merely control the reproduction volume, the quality of audio sound cannot be improved at all. In another approach, echo systems have been introduced in automotive audio systems to provide a better quality of sound, i.e. a better ambience. In typical automotive audio systems with such echo systems, the audio signals from an audio signal source, such as a radio, a magnetic tape recorder or a compact disk player, are separated into two components. One of the components is then sent to a mixer and the other is processed in an echo signal generator and then sent to the mixer. The mixer mixes the direct audio signal with the echo signal from the echo signal generator and sends the mixed signal to a main amplifier. Therefore, the echo signal produced by the echo signal generator is reproduced through a common main amplifier and a common speaker system with the direct audio sound. This system spoils the effect of the echo signal. In particular, in automotive audio systems, since the compartment is rather small and thus speaker or speakers are necessarily located near the listeners, echo systems in automotive audio systems have not been at all effective. Therefore, the need for higher quality audio sound and better ambience has not yet been satisfied.
Furthermore, although echos often enhance the quality of music, they make it harder to hear verbal announcements and program, such as news, conversation and so forth.